Tomorrow’s climate-friendly production will harvest solar energy and use CO2

ScienceViews 5. may 2021 6 min Professor Birger Lindberg Møller Written by Birger Lindberg Møller

Why not rethink our industrial production systems completely? Instead of being based on fossil fuels and release of immense amounts of CO2 into the atmosphere, they should be based on harvesting solar energy and the consumption of CO2. It would be far better for the climate – and it is becoming a realistic option.

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Climate change and its effects on our everyday lives is apparent to everyone. Fortunately, renewable energy sources like solar and wind energy can now provide cost competitive electricity. Yet fossil fuels are still used to cover 80% of the total global energy demand and sold at low prices. This severely hampers international efforts to reduce the global CO2 emissions. There is an urgent need for development and implementation of new climate-friendly production systems, not for patch solutions. We need innovative thinking to address the root of the problem!

The wonder of photosynthesis

But how do we turn the production system around? As a plant biochemist through a long life, I have repeatedly realized that if we look at the right places in nature – and for me it is especially in the world of plants – we find what we seek. This is also true now and is in fact quite straight forward. Because the production process we seek to harness is taking place right in front of us.

The process is photosynthesis and it is the basis of life on Earth. Organisms such as cyanobacteria (bacteria that perform photosynthesis), green algae and plants use solar energy and ambient CO2 to be self-sufficient through photosynthesis and the uptake of mineral salts.

In essence, we need to move from the current Anthropocene epoch – where humans are our planet’s paramount influencers – to the Planta-Algaecene epoch powered by plants and algae. Here, solar-driven production of biomass and natural compounds based on CO2 will become mainstream and the basis of a circular bioeconomy.

A fossil-free treasure chest

This new type of fossil-free production would produce the compounds and products that we already use in our everyday lives such as flavours (vanilla, cinnamon, hops), colours (carmine, indigo), stimulants (caffeine, cannabinoids), health promoting compounds (flavonoids, resveratrol), vitamins, and medicines (morphine, taxol). Importantly, it would also produce new high-value pharmaceutical compounds and new types of biodegradable polymers.

In addition to this, the production would provide additional amounts of biomass and biofuels to support the requied industrial transition.

Harvesting solar energy

The sun is by far our largest renewable energy source. The amount of solar energy hitting the Earth´s surface is per unit of time 5000 times higher than currently consumed by humanity.

This gives an obvious window of opportunity we must seek to benefit from. We can do so by understanding the diversity and uniqueness of nature and by developing photosynthesizing organisms into “green yeast cells” that can produce both biofuels and high-value natural compounds. They can all be powered solely by solar energy and – best of all – by using CO2 rather than emitting it.

The real game-changer: High-value compounds

Plants naturally produce medicinal compounds, dyes, flavorings, antioxidants, texture enhancers, proteins, carbohydrates and oils. Complementary production of the high value compounds can revolutionize future agricultural and pharmaceutical production. This will be the real game-changer!

Development of efficient parallel production of high-value natural products and commodities such as oils offers the opportunity to make the transition to solar energy based production economically viable within the next decade. This can help neutralizing the immediate initial direct costs associated with switching to a green production system – and simultaneously boost the sustainable production of inexpensive oil-containing biofuels.

Like in the development of wind turbines and solar cells, the pioneering attempts to use plants and algae as biomass for commercially viable production of biofuels have been met by severe setbacks and overselling. Now we have the knowledge to move into the successful development phase.

The pieces of the puzzle

The good news is that many of the pieces in this puzzle have now been identified. Research has cracked many of the codes for how to do this in relevant, economically viable and environmentally sound ways in close collaboration with nature itself.

In nature, cyanobacteria, algae and higher plants have inherent abilities, that make them the world’s best chemists. They use solar energy to produce everything they need themselves. From large quantities of carbohydrate, fat or protein to tiny amounts of thousands of different unique bioactive natural compounds, that the plant uses to sustain life and fend off attackers. These natural compounds often accumulate in complex mixtures, which makes them difficult and environmentally harmful to isolate. Furthermore, it often requires an incredible large number of plants – and thus agricultural land – to provide the quantities humans need. In that sense, the plants do not really care about us humans! As a consequence, the demands are often met by chemical synthesis from fossil resources.

In our research, we specialize in elucidating how high-value natural compounds are formed in nature and utilize this knowledge to develop specific cyanobacterial and algal strains to produce the compounds in large quantities as a sustainable replacement for the currently used fossil-based chemical synthesis.

Tomorrow’s photosynthetic world

Here, too, we can lean on nature. Cyanobacteria, algae and plants also produce all the raw materials, such as aromatic amino acids, isoprenoids and fatty acids, from which the many natural compounds are formed. We can use these same raw materials to synthesize the new natural compounds we want and need.

The production itself will take place in cyanobacteria and in the chloroplasts of algae and plants. This requires that we use genetic engineering to introduce the extra genes that encode the formation of the desired bioactive natural compound. In this way, we build on the inherent synthetic potential of the cyanobacteria and of the chloroplasts of algae and plants.

Moreover, a successful outcome requires careful considerations on the choice of production organisms, cultivation methods, upscaling and purification and the question of whether to use plants, algae or cyanobacteria.

Turning our Blue Planet into a Green World

Cultivating plants requires land. To avoid this, the green production may be located at sea using algae and cyanobacteria. More precisely, the production can take place in coastal waters in environmentally contained glass-covered basins constructed on floating platforms of about three hectares each. Using salt water as a culture medium reduces the risk of the culture pool being contaminated with other cyanobacteria and algae, since most species require fresh water to grow.

Other important criteria to consider when selecting cyanobacteria and algae as production organisms are their inherent ability to produce large amounts of proteins, carbohydrates or oils. In the latter case, the biomass can be used without costly processing as bunker fuels and cover the fuel needs of the global shipping industry.

For this, a key algae would be Nannochloropsis oceanica, which has an oil content exceeding 60% of its dry mass. Compared to other green oil sources, this algae can produce 60 times more oil per area unit than soybeans and about five times more than oil palms per year.

Parallel production of high and low value compounds

A crucial criteria is that the selected cyanobacteria or algae can be engineered to produce large quantities of a desired high-value natural compound. The algae cultures can then be cultivated by continually draining the green algae soup at the same rate as fresh filtered seawater is added to the basin. This enables production of both biomass and high-value compounds.

The biomass in the drained algae soup is then isolated and used as bunker fuel or protein source. The high-value compounds are isolated using two-phase systems and large-scale flash chromatography. The entire platform would be connected to wind turbines, which would power centrifuges and other equipment for extraction as well as supply energy to modify the algae soup by hydrothermal liquefaction, if so desired.

By encapsulating the basins on the floating platforms under a tight-fitting glass cover, the production system would be environmentally contained and comply with all European Union standards for cultivating genetically modified organisms.

Depending on which high-value natural products are desired, additional mineral salts or filtered wastewater may be pumped into the basin to add nutrients and speed up biomass production.

The direct - and indirect – costs of fossil fuels

Today, the direct costs of algae-based production of biofuels on floating platforms are higher than the current sales price of fossil fuel. However, the low fossil price does not account for the cost of their negative environmental impacts. A carbon tax needs to be implemented as an indispensable element in the global strategy to reduce CO2 emissions in an efficient way and spur environmentally benign bioproduction.

Denmark has the know-how – now investments are needed

Internationally, this development will require considerable direct investments over the next 10–15 years. For this, Denmark is well placed to participate. Based on our strong tradition in the shipbuilding industry, we have world-leading marine design competencies that can be used for constructing the offshore production platforms connected to wind turbines. This will create many jobs in Denmark outside the large cities.

Throughout the development phase, the use of advanced techno-economic model systems to fast track system optimization and de-risk the scale-up is essential to end up with robust business models. Accompanied by pilot scale-up trials, this serves to secure major investments.

To be successful, international collaboration is a must. Our partners in Australia, the US and elsewhere have unique and strong competences on selection and engineering of optimal cyanobacteria and algae species and have pioneered the development of advanced techno-economical model systems on how to drive the transition towards green production. Likewise, we are among the world leaders in synthetic biology research paving the way for production of many high-value natural compounds using cyanobacteria and algae as biological production systems.

So, let’s get going with the long-term investments!

Deciding to expand Denmark by constructing an energy island located 80 kilometres offshore in the North Sea is a step in the right direction.

Such an energy island could easily be surrounded by a large number of hectare-sized basins filled with highly productive cyanobacteria and algae and create the basis of a sustainable future both economically and environmentally feasible production system. We are ready!

The outlined approach will ultimately deliver economic, social and environmental benefits to Denmark. Globally it will help the international community to meet the sustainable development goals and to build circular economies that are capable of operating within our planetary boundaries.

In 2019, the Novo Nordisk Foundation awarded a grant to Birger Lindberg Møller, Professor, Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen for the research initiative “The Black Holes in the Plant Universe” addressing key issues in green production. 

We carry out basic research across the spectrum of plant biochemistry – from the single molecule level to the field – and translate the findings into...

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